Table saws are typically provided with a relatively large recessed throat opening in the table top surface through which the circular saw blade projects at various heights and angles selected by the user. The throat opening is typically filled by a throat plate insert which can be easily removed and changed as necessary. Most commonly, the original equipment of a throat plate provided with a table saw will have an elongated slot extending there through, somewhat larger than the kerf of the blade and having an elongate slot length slightly greater than the maximum chordal length of the portion of the saw blade extending above the saw table top surface at maximum height. The width of the elongate slot is typically larger than a conventional blade so that a table saw operator can install a thicker blade such as a carbide tip rip blade without interference. When a very thin kerf blade is installed, particularly at low blade height, very little of the elongated slot is filled with the portion of the blade extending above the height of the table which can pose a problem when cutting thin veneers or materials which easily chip. To address this problem, after market throat plates are available without any elongated slot formed therein at the time of the purchase. The user installs the throat plate on a table saw with the saw fully retracted and with the saw blade rotating raises the blade through the throat plate forming an elongate slot in situ. This type of throat plate is referred to as a "zero clearance throat plate".
Zero clearance throat plates are particularly useful when installing nonstandard diameter saw blades such as a dado head cutter which cuts slots having widths ranging from 1/8" to 3/16". Dado head cutters are frequently used to cut a groove in a workpiece having a precise width and depth. The width of cut is determined by the dado blade adjustment. The depth of the cut into the workpiece is determined by the blade height relative to the table. Blade height is typically set using a scale or blade height setting tool with a series of stepped notches formed therein. Accurately setting can be a tedious process frequently requiring trial and error and several iterations with requiring the user to make an initial cut, checking cut depth and adjusting accordingly.